1. Field of the Invention
The present invention relates to a serial communication apparatus and serial communication method to transmit and receive serial data through data signal lines.
2. Description of Related Art
In recent communication apparatus, the number of signal lines is reduced to save the cost. For example, the conventional synchronous serial communication method needed at least three lines of transmission line, receiving line and synchronous clock line, but in the recent communication method it has become possible to reduce to two lines of data line and synchronous clock line by controlling transmission and receiving by protocol.
In the serial communication method, data signals are released by using open drain port at transmission terminal, to prevent damaging the control circuit through collision of signals especially in the case of communication trouble.
However, in this kind of communication method, the problem is that waveform rounding signal level gradually increase is generated when the signal line becomes from the first level to the second level. As a result, a lot of time is necessary to fix data on the signal line, so even if the frequency of the synchronous clock is increased to make communication faster, it is slower than the conventional communication serial system having transmission and receiving signal lines separated.